Last Updated on July 15, 2023
Ocrad is an OCR (Optical Character Recognition) program based on a feature extraction method. It reads images in pbm (bitmap), pgm (greyscale) or ppm (color) formats and produces text in byte (8-bit) or UTF-8 formats.
The software also includes a layout analyser able to separate the columns or blocks of text normally found on printed pages.
Ocrad can be used as a standalone console application, or as a backend to other software. It’s mainly for research purposes.
Ocrad recognizes characters by its shape, and the reason it is so fast is that it does not compare the shape of every character against some sort of database of shapes and then chooses the best match. Instead of this, Ocrad only compares the shape differences that are relevant to choose between two character categories, mostly like a binary search.
- Uses the ISO 10646 character set internally which can represent over 2 thousand million characters.
- Pass text through filters. Ocrad provides both built-in filters and user-defined filters. Built-in filters are:
- –filter=letters – Forces every character that resembles a letter to be recognized as a letter. Other characters will be output without change.
- –filter=letters_only. This is the same as –filter=letters, but other characters will be discarded.
- –filter=numbers. This forces every character that resembles a number to be recognized as a number. Other characters will be output without change.
- –filter=numbers_only. This is the same as –filter=numbers but other characters will be discarded.
- –filter=same_height. This discards any character (or noise) whose height differs in more than 10 percent from the median height of the characters in the line.
- –filter=text_block. This discards any character (or noise) outside of a rectangular block of text lines.
- –filter=upper_num. This forces every character that resembles a uppercase letter or a number to be recognized as such. Other characters will be output without change.
- –filter=upper_num_mark. This is the same as –filter=upper_num’, but other characters will be marked as unrecognized.
- –filter=upper_num_only. This is the same as –filter=upper_num’, but other characters will be discarded.
- Cross-platform support – runs under Linux, FreeBSD, NetBSD, OpenBSD, and Mac OS X.
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